This invention relates to apparatus for automatically disengaging and engaging a vehicle transmission upon movement of a brake pedal thereof, and more particularly, to such apparatus which may be synchronized to provide properly timed disengagement and engagement of the transmission relative to the application and release of the brakes.
The invention is particularly applicable to loaders of the type in which an engine employed to power the vehicle for movement from place to place is also employed to provide power, often through hydraulic pumps, to raise and manipulate a bucket, fork or other material handling device carried by the vehicle. It has been recognized as desirable to employ a connection between a brake pedal of a loader and its transmission to neutralize the transmission automatically upon actuation of the brakes. This has the advantage of freeing the hands of the operator to manipulate the bucket controls, instead of actuating a transmission of clutch lever first, and also insures availability of the full power of the engine for manipulating the bucket without delay.
In accordance with this advantage, a number of loaders have employed a dual brake pedal arrangement, one of which applies the brakes only, and the other of which disengages or neutralizes the transmission while also applying the brakes. (See, for example, U.S. Pat. No. 3,050,165 to Day et al, U.S. Pat. No. 3,181,667 to Lohbauer et al, and U.S. Pat. No. 3,565,220 to Lammers et al, all assigned to the assignee of this application.) In such systems, the neutralizer valve is commonly actuated by fluid pressure from a vehicle pressure source upon movement of the brake pedal. A study of these patents reveals that each includes a relatively complex valving arrangement for actuating the neutralizer valve and synchronizing (i) such neutralizing of the transmission with the application of the brakes, and (ii) engagement of the transmission upon release of the brakes. Such systems, while having proven quite effective for use, are relatively complex and expensive. Consequently, to overcome these problems, it would be desirable to provide relatively simple, inexpensive mechanical means for actuating an also simple, inexpensive neutralizing valve.
In the design of such means certain problems have arisen. It has been found that, with a neutralizing valve having a valving element of relatively short stroke (which is generally the case) it is difficult to achieve proper synchronization of operation of the valve with operation of the brake pedal, so that disengagement and engagement of the transmission can be achieved at the proper point of application and release of the brakes. Another problem encountered is that of providing that the brake pedal is allowed to return freely to its released position, and be operated in a normal manner, without interference by such mechanical means.